Objectives: The purpose of this study is to examine the concepts of body image, self-esteem, mood states, and psychosocial functioning in- patients with Type I Gaucher's disease receiving enzyme replacement therapies. Methods: A repeated measures design was used in this study. Subjects were drawn from the population of patients with Type I Gaucher's disease who were concurrently enrolled in NINDS clinical research protocols evaluating the efficacy of enzyme replacement therapies. Measures of body image, self-esteem, mood states, and psychological functioning were obtained at select time intervals throughout the course of enzyme replacement therapy. Findings: Significant improvements in self-concept and a significant reduction in fatigue were found in patients with Gaucher's disease who participated in a one year trial of low dose enzyme replacement therapy. Patients who participated in the six month trial and received the recombinant form of enzyme replacement therapy demonstrated a significant reduction in tension, depression, anger, and fatigue. Significant changes in Sickness Impact Profile scores which incorporates both the physical and psychosocial dimension of illness were also found among these patients. Findings from this study demonstrated that changes in psychosocial functioning occurred in patients with Gaucher's disease receiving enzyme replacement therapy.